THEORY OF THE DEVELOPMENT OF ORGANISMS 129 



bees, and termites, have been slowly called into 

 existence by the operation of external influences 

 affecting the egg in its situation and food during 

 development. 



It has been shown fully by experiment and by 

 observation that the fertilised eggs of the queen 

 bee may become either workers or queens. This 

 depends merely on the cell in the hive in which 

 the egg is placed, and on what food the embryo is 

 reared. In the specially large cells, known as 

 queens' chambers, and with specially nutritious 

 diet, they become queens. With poor food, and 

 in smaller cells, they become workers. Even if 

 worker larvae be supplied in time with a richer 

 diet, they may be turned into queens. 



Similarly, the differences that exist among 

 termites and ants, as Emery shows, may be de- 

 scribed as polymorphism due to food. The Italian 

 zoologist, Grassi, has shown that termites have it 

 in their power to alter the relative numbers of 

 workers and soldiers, and to produce as many of 

 the latter as may be required, and they are able to 

 accelerate the sexual maturity of other individuals 

 by supplying nourishment suitable for stimulating 

 the maturation of the genital organs. 



Emery explains this polymorphism by attri- 

 buting it to the general laws of growth in the 

 insect organism under the influence of different 

 external stimuli. He thinks that ' the production 

 of workers depends upon a special capacity of the 

 germplasm to respond to the abundance or scanti- 

 ness of certain nutritive materials by a greater 



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